1. Field of the Invention
The present invention relates to an imaging apparatus having an image stabilizing function.
2. Description of the Related Art
In an imaging apparatus such as a digital camera and a video camera, an object image often vibrates caused by a camera shake. As a result, the image may become awkward to view. Recently, as high magnification lenses are mounted on cameras, the image vibration has come to highly stand out especially at a telephoto side.
A method for correcting a vibration of the image caused by the camera shake or the like applied from outside of the camera includes an optical image stabilizing system and an image sensor type system, and many imaging apparatuses including such functions have already been put into the market.
A method for detecting a vibration such as the camera shake, for example, includes a sensor method for detecting a vibration of the imaging apparatus due to the hand shake by using a vibration sensor, and a motion vector method for detecting a vibration based on a captured image. In the sensor method, usually an angular velocity sensor is used.
The angular velocity sensor vibrates a vibration material at a constant frequency, and converts a Coriolis force generated by a rotational motion component into a voltage to obtain angular velocity information. An image vibration correction is performed by performing integration on the obtained angular velocity information, calculating a vibration correction amount or a driving target position from a vibration output signal, and driving a correction unit by using the calculation result.
On the other hand, in the motion vector method, an image vibration is detected as a motion vector, by detecting an image of an object focused on an image sensor via an imaging lens, storing the image in a memory as an image signal, and comparing the image signal with the next detected image signal. The vibration correction amount is calculated from the calculated motion vector, and the image is corrected using the optical image stabilizing system or the image sensor type stabilizing system.
When using the image stabilizing function, a feedback control for feeding back a correction lens position signal to the vibration correction amount is performed in both methods.
Many methods and apparatuses for correcting the image vibration according to the vibration correction amount calculated using the vibration output signal obtained from the vibration sensor or the captured image signal are proposed. As the imaging apparatus is downsized, an optical system such as an imaging lens is also downsized, and an angle of view that can be imaged is also increasingly restricted.
Therefore, chances of attaching a conversion lens for changing a magnification of the imaging lens to take a wider angle image or a farther image increase. However, when attaching a high magnification zoom lens or conversion lens, for example, a correction amount obtained from a vibration applied to a camera may not correspond to a displacement to be corrected on the image.
In Japanese Patent Application Laid-Open No. 2005-203861, the following technique is discussed. That is, a gain adjustment value coefficient is calculated based on a vibration output signal generated based on a camera shake signal detected by the vibration sensor and a vibration output signal generated based on a motion vector detected by a motion vector detection unit. Then, by gain-controlling the vibration output signal from the vibration sensor by using a vibration correction gain set based on the gain adjustment value coefficient, the effect of an image vibration correction function is improved.
The vibration correction gain is adjusted for adjusting an output variation due to variation of the individual vibration sensor, an environmental change, and a deterioration of the vibration sensor with age, so that the vibration output signal of the vibration sensor becomes constant for a predetermined camera shake.
However, in the conventional example, when calculating the gain adjustment value coefficient based on a motion vector including a camera vibration when imaging a moving object, an appropriate vibration correction gain cannot be obtained and a sufficient image vibration correction effect cannot be obtained in a captured image.
When calculating the gain adjustment value coefficient in a panning operation of the imaging apparatus, an appropriate vibration correction gain cannot be obtained during and just after the panning operation. Therefore, a sufficient image vibration correction effect cannot be obtained for an image captured during and just after the panning operation.
In the conventional example, since a calculation for setting the vibration correction gain is kept performing other than when the vibration correction gain changes after setting the vibration correction gain, an unnecessary calculation load is applied to a calculation processing unit.